How to install "dig": -bash: /usr/bin/dig: No such file or directory

If you are missing the dig command it means you are missing a package called bind-utils.  To install this package use yum to install bind utils:

yum install bind-utils

Or if you do not have access to yum, maybe from a hosted VPS solution you can grab the RPM packages (this is 100% assuming you are CentOS):

rpm -i http://mirror.centos.org/centos/5/os/i386/CentOS/bind-utils-9.3.4-6.P1.el5.i386.rpm

Or maybe you want to install the entire bind/named system:

rpm -i http://mirror.centos.org/centos/5/os/i386/CentOS/bind-9.3.4-6.P1.el5.i386.rpm
rpm -i http://mirror.centos.org/centos/5/os/i386/CentOS/bind-chroot-9.3.4-6.P1.el5.i386.rpm
rpm -i http://mirror.centos.org/centos/5/os/i386/CentOS/bind-libs-9.3.4-6.P1.el5.i386.rpm
rpm -i http://mirror.centos.org/centos/5/os/i386/CentOS/caching-nameserver-9.3.4-6.P1.el5.i386.rpm
rpm -i http://mirror.centos.org/centos/5/os/i386/CentOS/bind-utils-9.3.4-6.P1.el5.i386.rpm
[ centos ]